Chmod Calculator

Free online tool. All processing is client-side. No signup needed.

How to Use the Chmod Calculator

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Chmod Calculator?

A CHMOD Calculator converts between octal Unix file permissions (755, 644) and symbolic representation (rwxr-xr-x). Every file and directory on Unix systems has permission bits controlling read, write, and execute access for owner, group, and others. This calculator translates between numeric and symbolic notation and explains exactly what each setting means.

How Does It Work?

Enter a numeric permission or click r/w/x checkboxes for Owner, Group, and Others. The calculator shows: octal number, symbolic representation, binary bits, and a plain-English description. Presets: 755 (directories/scripts), 644 (files), 700 (private), 600 (SSH keys).

Formula

Read=4, Write=2, Execute=1. Sum per category: Owner 7=rwx, Group 5=r-x, Others 5=r-x = 755\nCommon: 755 (rwxr-xr-x), 644 (rw-r--r--), 700 (rwx------), 600 (rw-------)\nSpecial: SUID (4###), SGID (2###), Sticky (1###)\nExecute on dir = can enter; execute on file = can run

Who Uses This Tool?

• Linux/macOS users setting file permissions with chmod command
• System administrators securing web server file permissions
• Developers troubleshooting 'permission denied' errors
• Anyone learning Unix file system permissions

Pro Tips

• Never use chmod 777 — it makes files world-writable. The #1 cause of web server compromises
• Web server: directories=755, files=644. Never give web server write access to code files
• SSH keys MUST be 600 (owner read/write only). SSH refuses keys with group/other permissions

Frequently Asked Questions about Chmod Calculator

What does chmod 755 mean?

Owner: full (7=rwx). Group: read+execute (5=r-x). Others: read+execute (5=r-x). Standard for directories and executable scripts.

Why is 777 dangerous?

Every user can read, write, and execute. Any compromised process can modify/delete your files. Use only for /tmp with sticky bit.

Free online Chmod Calculator — no signup, 100% client-side processing. All data stays in your browser.